Spinal implant

ABSTRACT

A spinal implant is disclosed which when placed within the spinal disc space stabilizes the spinal segment.

This is a continuation application Ser. No. 09/580,768, filed May 30,2000, now U.S. Pat. No. 6,478,823; which is a continuation-in-part ofapplication Ser. No. 29/056,996, filed Jul. 15, 1996, now U.S. Pat. No.D425,989; which is a continuation of application Ser. No. 29/023,922,filed Jun. 3, 1994, now abandoned; which is a continuation ofapplication Ser. No. 08/052,211, filed on Apr. 22, 1993, now abandoned;which is a continuation of application Ser. No. 07/546,849, filed Jul.2, 1990, now abandoned; which is a continuation of application Ser. No.07/212,480, filed Jun. 28, 1988, now abandoned; all of which areincorporated herein by reference.

BACKGROUND

The present invention relates to an artificial fusion implant to beplaced into the intervertebral space left after the removal of a damagedspinal disc.

The purpose of the present invention is to provide an implant to beplaced within the intervertebral disc space and provide for thepermanent elimination of all motion at that location. To do so, thedevice is space occupying within the disc space, rigid, self-stabilizingto resist dislodgement, stabilizing to the adjacent spinal vertebrae toeliminate local motion, and able to intrinsically participate in avertebra to vertebra bony fusion so as to assure the permanency of theresult.

At present, following the removal of a damaged disc, either bone ornothing is placed into the space left. If nothing is placed in the spacethe space may collapse which may result in damage to the nerves; or thespace may fill with scar tissue and eventually lead to a reherniation.The use of bone is less than optimal in that the bone obtained from thepatient requires additional surgery and is of limited availability inits most useful form and if obtained elsewhere, lacks living bone cells,carries a significant risk of infection, and is also limited in supplyas it is usually obtained from young accident victims. Furthermore,regardless of the source of the bone, it is only marginal structurallyand lacks a means to either stabilize itself against dislodgement, or tostabilize the adjacent vertebrae.

A review of all possibly related prior art will demonstrate the noveltyof the present invention.

There have been an extensive number of attempts to develop an acceptabledisc prothesis (an artificial disc). Such devices by design would beused to replace a damaged disc and seek to restore the height of theinterspace and to restore the normal motion of that spinal joint. Nosuch device has been found that is medically acceptable. This group ofprosthetic or artificial disc replacements seeking to preserve spinalmotion which are different from the present invention include:

U.S. Pat. No. 3,867,728 STUBSTAD—describing a flexible disc implant.

U.S. Pat. No. 4,349,921 KUNTZ—describing a flexible disc replacementwith rope or file like surface projections to discourage devicedislocation.

U.S. Pat. No. 4,309,777 PATIL—describing motion preserving implant withspice outer surfaces to resist dislocation and containing a series ofsprings to urge the vertebrae away from each other.

U.S. Pat. No. 3,875,595 FRONING—describing a motion preserving bladderlike disc replacement with two opposed stud like projections to resistdislocation.

U.S. Pat. No. 2,372,622 FASSIO (French)—describing a motion preservingimplant comprising complimentary opposed convex and concave surfaces.

In summary then, these and other similar devices resemble the presentinvention only in that they are placed within the intervertebral spacefollowing the removal of a damaged disc. In that they seek to preservespinal motion, they are diametrically different from the presentinvention which seeks to permanently eliminate all motion at that spinalsegment.

A second related area of prior art includes those devices utilized toreplace essentially wholly removed vertebra. Such removal is generallynecessitated by extensive vertebral fractures, or tumors, and is notassociated with the treatment of disc disease, or therefore related tothe present invention. While the present invention is to be placedwithin the disc space, these prior devices cannot be placed within thedisc space as at least one vertebra has already been removed and thereno longer remains a “disc space.” Furthermore, all of these devices arelimited in that they seek to perform as temporary structural membersmechanically replacing the removed vertebra (not a removed disc), and donot intrinsically participate in supplying osteogenic material toachieve cross vertebrae bony fusion. Therefore, again unlike the presentinvention which provides for a source of osteogenesis, use of this groupof devices must be accompanied by a further surgery consisting of a bonefusion procedure utilizing conventional technique. This group consistingof vertebral struts rather than disc replacements would include thefollowing:

U.S. Pat. No. 4,553,273 WU—describing a turnbuckle like vertebral strut.

U.S. Pat. No. 4,401,112 REZAIAN—describing a turnbuckle like vertebralstrut with the addition of a long stabilizing staple that spans themissing vertebral body.

U.S. Pat. No. 4,554,914 KAPP—describing a large distractible spike thatelongates with a screw mechanism to span the gap left by the removal ofa entire vertebrae and to serve as an anchor for acrylic cement which isthen used to replace the missing bone (vertebrae).

U.S. Pat. No. 4,636,217 OGILVIE—describing a vertebral strut mechanismthat can be implanted after at least one vertebra has been removed andwhich device consists of a mechanism for causing the engagement ofscrews into the vertebra above the vertebra below the one removed.

In summary then, this group of devices differs from the presentinvention in that they are vertebral replacement struts, do notintrinsically participate in the bony fusion, can only be inserted inthe limited circumstances where an entire vertebra has been removed fromthe anterior approach, and are not designed for, or intended to be usedfor the treatment of disc disease.

A third area of prior art related to the present invention includes alldevices designed to be applied to one of the surfaces of the spine. Suchdevices include all types of plates, struts, and rods which are attachedby hooks, wires, and screws. These devices differ significantly from thepresent invention in that they are not inserted within the disc space,and furthermore do not intrinsically participate in supplying osteogenicmaterial for the fusion.

Therefore, with these devices where permanent spinal immobilization isdesired an additional surgery consisting of a spinal fusion performed byconventional means or the use of supplemental methylmethacrylate cementis required. Such devices, applied to the spine but not within the discspace, would include the following:

U.S. Pat. No. 4,604,995—STEPHENS—describing a “U” shaped metal rodattached to the posterior elements of the spine with wires to stabilizethe spine over a large number of segments.

U.S. Pat. No. 2,677,369—KNOWLES—describing a metal column device to beplaced posteriorly along the lumbar spine to be held in position by itsshape alone and to block pressure across the posterior portions of thespinal column by locking the spine in full flexion thereby shifting themaximum weight back onto the patient's own disc.

Other devices are simply variations on the use of rods (e.g. Harrington,Luque, Cotrel-Dubosset, Zielke), wires or cables (Dwyer), plates andscrews (Steffee), or struts (Dunn, Knowles).

In summary, none of these devices are designed for or can be used withinthe disc space, do not replace a damaged disc, and do not intrinsicallyparticipate in the generation of a bony fusion.

Other prior art possibly related to the present invention and therefore,to be considered related to “Bony Ingrowth”. Patents related to thisfeature describe either methods of producing materials or devices toachieve the same. Such patents would include:

U.S. Pat. No. 4,636,526 (DORMAN), U.S. Pat. No. 4,634,720 (DORMAN), U.S.Pat. No. 4,542,539 (ROWE), U.S. Pat. No. 4,405,319 (COSENTINO), U.S.Pat. No. 4,439,152 (SMALL), U.S. Pat. No. 4,168,326 (BROEMER), U.S. Pat.No. 4,535,485 (ASHMAN), U.S. Pat. No. 3,987,499 (SCHARBACH), U.S. Pat.No. 3,605,123 (HAHN), U.S. Pat. No. 4,655,777 (DUNN), U.S. Pat. No.4,645,503 (LIN), U.S. Pat. No. 4,547,390 (ASHMAN), U.S. Pat. No.4,608,052 (VAN KAMPEN), U.S. Pat. No. 4,698,375 (DORMAN), U.S. Pat. No.4,661,536 (DORMAN), U.S. Pat. No. 3,952,334 (BOKROS), U.S. Pat. No.3,905,047 (LONG), U.S. Pat. No. 4,693,721 (DUCHEYNE), U.S. Pat. No.4,070,514 (ENTHERLY).

However, while the present invention would utilize bone ingrowthtechnology, it would do so with conventional technology.

The final area of related prior art to be considered is that of devicesdesigned to be placed within the vertebral interspace following theremoval of a damaged disc, and seeking to eliminate further motion atthat location.

Such a device is contained in U.S. Pat. No. 4,501,269—BAGBY describingan implantable device, limited instrumentation, and a method; whereby ahole is bored transversely across the joint and then a hollow metalbasket of larger diameter is then pounded into the hole and then filledwith the bone debris generated by the drilling. The present inventiondiffers from the prior art devices in the following ways:

1. UNIVERSAL APPLICABILITY WITHOUT CONTOURING OF THE INTERSPACE. Thepresent device will fit any patient, anywhere throughout the spine, inany intervertebral disc space, and without alteration of that interspaceregardless of its natural size or shape.

2. RESTORATION AND PRESERVATION OF THE INTERSPACE. The present inventionwill restore the intervertebral space to its premorbid dimensions, anddo so by having the implant fit the space rather than having to modifythe interspace, by bone removal from the vertebrae, to accommodate theimplant.

3. END PLATE PRESERVATION. Preservation of the highly specialized weightbearing cortical bone is allowed and end plate perforation into thehighly vascular cancellous bone marrow with its attendant bleeding isavoided. Such bleeding, when it occurs, bears all the risks of bloodloss (e.g. hypovolemic shock, transfusion transmitted diseases such ashepatitis and acquired immune deficiency syndrome, etc.), and all thecomplications arising from the resultant impaired visualization of thevital structures (e.g. nerves, blood vessels, and organs) due to suchbleeding.

4. TECHNIQUE. The technique for insertion of these implants isconsistent with the established methods of disc removal, and requiresneither specialized instrumentation nor specialized surgical technique.

5. EXTENT OF DISC REMOVAL. The extent of disc removal can be determinedby the surgeon at the time surgery and can be individualized for eachpatient.

6. NO DRILLING. No drilling is involved with the use of the presentinvention.

7. ELIMINATION OF INCORRECT IMPLANT SIZE SELECTION. In those implantsystems where a drill is used and significant bone is removed then anestimate of the implant size must first be made, and then, regardless ofthe fit, an implant at least as large as the space created by thedrilling must be utilized, regardless of the quality of that fit. Withthe present invention no significant bone is removed, and the correctsize implants are fitted directly to the interspace eliminating the needto guess at the correct implant size before the fact.

8. MODULAR DESIGN. The present implants are available in varying lengthsto accommodate the changing depths of the interspace from central tolateral. The devices are available in varying heights or are infinitelyadjustable as to the height within the physiological range. The widthsare standardized, and the various embodiments can be used in anycombination (e.g. in the lumbar spine two auto-expanding implants couldbe used in conjunction with two anchor deploying implants to completelyfill the interspace).

9. AVOIDANCE OF SIZE LIMITATIONS. Because in one embodiment the systemis modular, component parts can be inserted through a very small openinguntil a much larger implant is reconstituted completely filling theavailable interspace; and yet much larger when assembled than theopening through which the component modular sections were introduced.For example, in the lumbar spine four implants introduced one at a timeand measuring 8 mm in width, would when reconstituted within theinterspace constitute a 32 mm wide implant. Implantation of a singleimplant of those dimensions from a posterior approach in the lumbarspine would otherwise be impossible because of the presence of the duralsac and spinal nerves.

10. THE AVOIDANCE OF INTERSPACE COLLAPSE. The device is many timesstronger than bone and will not collapse. The implantation of the deviceallows preservation of the very strong vertebral cortex, which isresistant to compression preventing the migration of the implant intothe vertebrae. The large surface area of the assembled modular implant,minimizes the load per unit area. For example, a reconstituted lumbarimplant of four modular components would have the weight distributedover approximately 8 sq. cm. per vertebral interface.

11. REMOVABILITY. Because the present invention is an interspace implantand not a “through vertebrae” cross interspace implant, removal of theimplant, should that become necessary, would not result in iatrogenicdestruction of the adjacent vertebrae.

12. SELF-STABILIZING. The implant is self-stabilizing without the use ofthreads. All of the implants are surface configured to resistdislodgement and the preferred embodiments contain active, mechanicalmeans to assure permanent anchoring. Long term stability begins with theabove and is further enhanced by surface treating of the implant forbone ingrowth (by known conventional means) and osteogenically loadingthe implants.

13. SPINE REDUCING. Various embodiments of the present invention such asthe ones with the 180 degree opposed ratcheted surface, and theauto-expanding type, are capable of reducing a vertebral listheses (aforward or backward translation of one vertebrae upon another).

14. SPINAL STABILITY. These implants are capable of stabilizing a spinalsegment following disc removal, and do so without the use of threads(threads would by design need to violate the vertebrae themselvesextensively).

15. SAFETY. The entire procedure is performed under direct vision andwith complete visualization of the adjacent vital structures (e.g.organs, neural structures and blood vessels).

In summary then, the present invention is an interspace implant utilizedto replace a damaged disc, which unlike an artificial disc, seeks topermanently eliminate rather than to preserve spinal motion, and to doso by a bony fusion. The present invention is clearly an improvementover the prior art providing an interspace implant intrinsicallyparticipating in the fusion process, self-stabilizing, stabilizing tothe spinal segment, consistent with conventional methods of discectomy,and uniquely consistent with the preservation of the integrity of theadjacent vertebrae.

BRIEF SUMMARY OF THE PRESENT INVENTION

The present invention comprises an artificial implant, the purpose ofwhich is to participate in, and directly cause bone fusion across anintervertebral space following the excision of a damaged disc. Saidimplants are structurally load bearing devices, stronger than bone,capable of withstanding the substantial forces generated within thespinal interspace. Such devices have a plurality of macro sized openingsof 1–3 mm, which can be loaded with fusion promoting materials, such asautogenous bone, for the purpose of materially influencing the adjacentvertebrae to perform a bony bond to the implants and to each other. Theimplant casing may be surface textured or otherwise treated by any of anumber of known technologies to achieve a “bone ingrowth surface” tofurther enhance the stability of the implant and to expedite the fusion.Further, said devices are so configured and designed so as to promotetheir own stability within the vertebral interspace to resistdislodgement, and furthermore, to stabilize the adjacent vertebrae.

To use the implant of the present invention a conventional discectomy isperformed and the vertebral endplates scraped, but not perforated. Theappropriately sized implants are loaded with autogenous bone andimplanted within the interspace.

For example for an anterior cervical device implantation, a shorttransverse incision is made across the front of the neck and to theright of the midline directly over the diseased disc. The platysmamuscle is split, and the sternocleidomastoid muscle with the carotidsheath is protected and retracted laterally. The esophagus, trachea andassociated midline structures are protected and retracted medially, thusexposing the anterior aspect of the cervical spine. The diseased disc isidentified and removed by conventional surgical methods. The adjacentvertebral endplates are gently scraped free of any remaining cartilageuntil diffuse fine punctuate decortication is achieved. The dimensionsof the interspace are then measured In mold distraction, and theappropriate implant selected. Cancellous bone, obtained from thepatient's iliac crest or the equivalent, is loaded into the implant. Thesafety driver is then utilized to insert the implant behind the anteriorlips of the vertebrae. The wound is then closed in the routine manner.

OBJECTS OF THE PRESENT INVENTION

It is an object of the present invention to provide for a means ofachieving interspace fusion and stabilization as a single procedure by ameans consistent with the conventional method of discectomy.

It is another object of the present invention to provide for a means ofachieving an interspace fusion and stabilization that is quicker, safer,and entails less blood loss than by any other known means.

It is another object of the present invention to provide for a means ofachieving a one stage interspace fusion and stabilization withoutsignificant violation or removal of the adjacent vertebral bone stock.

It is another object of the present invention to provide for a method ofintervertebral arthrodesis and stabilization of enhanced safety wherethe entire procedure is performed under direct vision.

It is another object of the present invention to provide for a method ofintervertebral arthrodesis and stabilization of greater simplicity andrequiring minimal specialized instrumentation or technique not alreadypossessed by those doing such procedures by conventional means.

It is another object of the present invention to provide for a modularprosthesis, allowing complimentary subunits to be inserted individuallythrough a small opening and to then be reassembled within theinterspace, so as to reconstitute an interspace occupying device muchlarger than would be insertable as a whole.

It is another object of the present invention to provide for a modularimplant system such that it is possible to precisely fit the contours ofany interspace without the need to sacrifice any vertebral bone toaccommodate the prosthesis. These and other objects of the presentinvention will be apparent from review of the following specificationsand the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top right perspective view of the implant (cervical type).

FIG. 1 a is a front view of the implant of FIG. 1

FIG. 1 b is a rear view of the implant of FIG. 1.

FIG. 1 c is a top view of the implant of FIG. 1.

FIG. 1 d is a side view of the implant of FIG. 1.

FIG. 1 e is a bottom view of the implant of FIG. 1.

FIG. 2 is a side sectional view of the implant viewed along lines 2—2 ofFIG. 1 d.

FIG. 3 is the implant FIG. 1 showing the attachment to the driver anddriver.

FIG. 4 is a front perspective view showing the implant being driven intothe disc space.

FIG. 4 a is a front perspective view of the implant located in thespine.

FIG. 5 is a side view of the implant in the spine attached to thedriver.

FIG. 5 a is a close up partial sectional view of the implant and driver.

FIG. 6 is a perspective view of a series of implants placed in a lumberintervertebral space.

FIG. 6A is an alternative embodiment of a rectangular solid implant.

FIG. 7 is a side sectional view of the vertebrae and implant viewedalong lines 7—7 of FIG. 6.

FIG. 7A is a side sectional view of the vertebrae structure showing athird embodiment of the rectangular solid implant in place.

FIG. 8 is an exploded perspective view of another embodiment of thepresent invention.

FIG. 9 is a side sectional view of the vertebrae structure and implantviewed along lines 9—9 of FIG. 8.

FIG. 10 is a side sectional view of the implant of FIG. 8, in acontracted position.

FIG. 11 is a side sectional view of the implant of FIG. 10, in anexpanded position.

FIG. 12 is a perspective view of an alternative embodiment of theimplant of FIG. 9.

FIG. 13 is an alternative embodiment of a hollow rectangular solidimplant.

FIG. 14 is a cross sectional view of the hollow rectangular solidimplant of FIG. 13 viewed along lines 14—14 of FIG. 13.

FIG. 15 is an alternative embodiment of an expandable implant in itsextended position.

FIG. 16 is an expandable implant of FIG. 15 in its retracted position.

FIG. 17 is an expandable implant of FIG. 16 located in the disc space.

Referring to FIGS. 1 through 5 an implant for use in the disc space andassociated apparatus used for inserting the implant 10 is shown. Theimplant 10 is shown as a substantially rectangular hollow configuration,having a tapered forward portion.

The implant 10 has an upper surface 12 and a parallel lower surface 14.The two side walls 16 and 18 are parallel to one another and have aseries of small sized openings 20 of 1 mm–3 mm through the side walls 16and 18.

The front wall 22 is slightly convex and has a depressed portion 24 witha central threaded opening 26 for receiving the engaging end 28 of adriving member 30.

The upper surface 12 has a threaded cap 32, which has opening 33 therethrough, with a central wrench opening 34 for engagement with an ALLENhex key wrench A of FIG. 3. The cap 32 covers the opening into thehollow implant 10 and permits the insertion of autogenous bone materialinto the hollow portion of the implant 10. The cap 32 is surrounded by aseries of small sized openings 36 of 1 mm to 3 mm passing through theupper surface and into the central hollow portion of the implant 10.

The rear wall 38 is convex so as to conform to the rear of the discspace.

The driving member 30, shown in FIG. 3, comprises a substantially hollowtubular member 40 having a long internal rod 42 having a turning knob 44at one end and a threaded portion 46 at the other end for threadablyengaging the threaded opening 26 of the implant 10. The engaging end 28of the driving member 30 has a slightly convex surface to complement theslightly convex surface of the front wall 22. The engaging end 28 has anextension 48 for fitting within the depressed portion 24 on the frontwall 22 of the implant 10. The engaging end 28 also has restrictionmembers 47 and 49 to restrict the depth of penetration of the driver 30.

In use, the cap 32 is removed from the implant 10 and autogenous bonematerial is inserted into the hollow portion of the implant 10. The capis then replaced. Various methods of packing the implant 10 with theautogenous bone material may be used to obtain a completely packedimplant 10.

Referring to FIGS. 4, 4 a, 5 and 5 a, the method of inserting theimplant is shown. The threaded end 46 of the internal rod 42 of thedriving member 30 is attached to the threaded opening 26 of the implant10 by turning of the knob 44. Once the engaging end 28 is in place, thefitting of the extended portion 48 into the depressed portion 24prevents movement of the implant 10 in relationship to the drivingmember 30.

The implant is then placed at the entrance to the disc space between thetwo adjacent vertebrae V. The knob 44 is then tapped with hammer 11sufficiently hard enough to drive the implant 10 into the disc space.The restriction members 47 and 49 which are wider than the disc space,prevent over penetration of the implant.

The size of the implant 10 is substantially the same size as the discspace that it is replacing and thus will be larger or smaller dependingon the disc space in which it is to be used. In the preferred embodimentthe implant 10 is approximately 13 mm wide.

Referring to FIGS. 4A and 5 the implant 10 is shown in place in the discspace after removal of the driving member once the implant was insertedin place.

The autogenous bone material that was packed within the hollow portionof the implant 10 serves to promote bone ingrowth between the implantand the adjacent vertebrae. Once the bone ingrowth occurs, the implant10 will be a permanent fixture preventing dislodgement of the implant aswell as preventing any movement between the adjacent vertebrae.

Referring to FIG. 6 an alternative embodiment of the implant isdisclosed. The implant 61 comprises a substantially rectangular memberhaving a series of ridges 62 on the upper and lower surfaces of theimplant 60. One or more grooves 64 are placed on the upper and lowersurfaces as well. As indicated in FIG. 6, a series of such implants 61are used as the interbody spinal implant, each placed closely adjacentone another to approximate the size of the removed disc. A series ofmicro sized openings 63 perforate the implant 61, to promote boneingrowth.

The implant of FIG. 6 is inserted as follows: the disc is substantiallyremoved by conventional means. The implants 61 are then inserted in theintervertebral space between the two vertebrae.

The size of the implant 61 of FIG. 6 is approximately 26 millimeters inlength and is wide enough so that four of them will substantially fillthe intervertebral space, depending on which vertebras are fused.

In FIG. 6 a a “bullet nosed” implant 67 having a open front portion 69to facilitate insertion of implant 67 is shown.

Referring to FIGS. 7 and 7 a alternative embodiments of the implant 61of FIG. 6 is shown in place between two vertebrae V.

In FIG. 7 the implant 70 is shown with the ridges 62 shown in the formof teeth facing the anterior. These ridges serve to prevent the implant60 from ‘walking’ out of the space between the vertebrae.

In FIG. 7 a an embodiment of the implant 70 of FIG. 6 is shown havingopposed ridges 72 and 74. This serves to maintain the alignment of thevertebrae when the two vertebrae V are improperly aligned with respectto one another.

Referring to FIG. 8 an adjustable implant 81 having means for adjustingthe width of the implant 81 is shown. The implant 81 comprises a lowermember 82 and an upper member 84 which when fitted together form anessentially rectangular implant. The upper member 84 and the lowermember 82 have hollow portions that face one another and receive taperedwedges 86 and 88 that fit within the hollow portion of the upper andlower members 82 and 84. The wedges 82 and 84 are such that at theirlarge and they are higher than the combined hollow space between theupper and lower members 84 and 82, and shallower at the other end thanthe hollow space between the upper and lower members.

The wedges 86 and 88 have a central threaded opening 90 and 92 inalignment with each other for receiving threaded screw 94. Deformableburrs 95 on the head 98 of the screw 94 are used for locking the screwin place. The implant has a series of holes 100 throughout the body ofthe implant to assist in the ingrowth process.

Referring to FIGS. 9 through 11 the expandable implant 81 is shownpositioned between the two vertebrae V. In FIG. 10 the expandableimplant 81 is illustrated in its contracted position. The wedges 86 and88 abutt the interior sloped surfaces 104 of the upper and lower members82 and 84.

As the screw 94 is turned, as shown in FIG. 11, the wedges 86 and 88 aredrawn together, and the sloped portions of the wedges force the uppermember 82 away from the lower member 84. Once the screw 94 has beenturned sufficiently, the screw head 98 is hit, causing the deformableburrs to be crimped so as to prevent the reverse rotation of the screw94.

In FIG. 12, another alternative embodiment of the expandable implant 81is illustrated with spike projections 106 extending from the top andbottom members to dig into the vertebrae and assist in maintaining it inplace.

In use, the disc is removed, and the implant 81 is placed between thevertebrae. The screw 94 is then turned expanding the implant. In thepreferred embodiment, the width is from 8 millimeters to 18 millimeters.

Referring to FIGS. 13 and 14, another alternative embodiment of theinvention is shown in which the implant 200 comprises a rectangularhollow member having a slightly tapered forward section 202. The crosssection, shown in FIG. 14, shows the rectangular configuration of theimplant.

In use of the implant the interior of the implant is filled with a pastemade of autogenous bone, and inserted in the place of the former disc.The strength of the material used to make the implant is such that, eventhough it is substantially hollow, it does have sufficient strength towithstand the forces of the vertebrae compressing the implant.

Referring to FIGS. 15–17, another alternative embodiment is shown inwhich the implant has movable projections which are movable from a firstposition within the implant to a second position extending outside ofthe implant.

The implant 300 is of a generally rectangular configuration. The topsurface 302 and the bottom surface 304 of the implant have slots 306 forpermitting pivotal member 307 having spikes 308 at their ends to projectthrough said slots 306. The spikes 308 are pinned at one end 310 withinthe implant 300.

Opposing wedge shaped members 312 and 314 having a central threadedopening 316 for receiving a threaded screw 318 having a head 320 and aslot 322. The wedges are facing each other so that upon turning of thescrew will draw the two wedges together, causing the wedges to cause thespikes 308 to pivot about their end 310 and cause the spikes to projectout of the implant through the aligned slots 306. The depressions 329 inthe pivotal member 307 engage the wedges 314 and 312 to lock the pivotalmembers 307 in place. A series of holes 324 for promoting bone ingrowthand fusion are provided in the implant 300.

In use, after the removal of the disc material, the implants with thespikes 308 in their withdrawn position, are inserted into the discspace. Then the screw 318 is turned until the spikes 308 are forced toenter the vertebrae material, as shown in FIG. 17. The implant 300 isthus held firmly in place.

These implants have a surface configuration so as to induce boneingrowth through the implant, and into the wall of the vertebrae ineffect inducing fusion from one vertebrae V to the other, therebyeventually making the implant itself superfluous as the bone would dothe work.

The implant itself, because of its being made of stronger material thanbone, would provide structural support to the two vertebrae whileawaiting bone ingrowth. Once the bone ingrowth occurred, however, theimplant would be firmly and permanently fixed in place.

While the invention has been described with regards to the preferredembodiment and a number of alternative embodiments, it is recognizedthat other embodiments of the present invention may be devised whichwould not depart from the scope of the present invention.

1. A spinal fusion implant comprising: a leading end and a trailing endopposite said leading end, said implant having a length from saidleading end to said trailing end, said trailing end having a perimeter,said trailing end having a hole therein, said trailing end having a slotportion intersecting one portion of the perimeter of said trailing end,said trailing end having another slot portion intersecting anotherportion of the perimeter of said trailing end opposite said one portionof the perimeter of said trailing end; opposite sides between saidleading and trailing ends, said implant having a width from one of saidsides to the other of said sides, said implant having a height; and anopening through said implant and oriented along the height, said openingbeing between said opposite sides and between said leading and trailingends.
 2. The implant of claim 1, wherein said slot portion and saidanother slot portion are opposite ends of a slot having a length and awidth transverse to the length of said slot.
 3. The implant of claim 2,wherein said hole has a diameter, the width of said slot being greaterthan the diameter of said hole.
 4. The implant of claim 2, wherein saidslot of said trailing end is rectangular.
 5. The implant of claim 2,wherein the length of said slot is greater than the width of said slot.6. The implant of claim 2, wherein said slot has a depth perpendicularto the length and the width of said slot, the width of said slot beinggreater than the depth of said slot.
 7. The implant of claim 1, whereinsaid hole is threaded.
 8. The implant of claim 2, wherein said hole hasa diameter, the diameter of said hole being less than one half thelength of said slot.
 9. The implant of claim 1, wherein said sides haveat least one opening in communication with said opening through theheight of said implant.
 10. The implant of claim 1, wherein said implantcomprises a second opening through said implant and oriented along theheight, said second opening being between said opposite sides andbetween said leading and trailing ends.
 11. The implant of claim 1,wherein the height of said implant is less than the width of saidimplant.
 12. A spinal implant comprising: a leading end and a trailingend opposite said leading end, said implant having a length from saidleading end to said trailing end, said trailing end having a perimeter,said trailing end having a hole therein, said trailing end having a slotportion intersecting one portion of the perimeter of said trailing end,said trailing end having another slot portion intersecting anotherportion of the perimeter of said trailing end opposite said one portionof the perimeter of said trailing end; opposite sides between saidleading and trailing ends, said implant having a height perpendicular tothe length of said implant; and said implant having a generallyrectangular cross section along at least a portion of the length of saidimplant.
 13. The implant of claim 12, wherein said slot portion and saidanother slot portion are opposite ends of a slot having a length and awidth transverse to the length of said slot.
 14. The implant of claim13, wherein said hole has a diameter, the width of said slot beinggreater than the diameter of said hole.
 15. The implant of claim 13,wherein said slot of said trailing end is rectangular.
 16. The implantof claim 13, wherein the length of said slot is greater than the widthof said slot.
 17. The implant of claim 13, wherein said slot has a depthperpendicular to the length and the width of said slot, the width ofsaid slot being greater than the depth of said slot.
 18. The implant ofclaim 12, wherein said hole is threaded.
 19. The implant of claim 13,wherein said hole has a diameter, the diameter of said hole being lessthan one half the length of said slot.
 20. The implant of claim 12,further comprising an opening through said implant and oriented alongthe height, said opening being between said opposite sides and betweensaid leading and trailing ends.
 21. The implant of claim 20, whereinsaid sides have at least one opening in communication with said openingoriented along the height of said implant.
 22. The implant of claim 20,wherein said implant comprises a second opening through said implant andoriented along the height, said second opening being between saidopposite sides and between said leading and trailing ends.
 23. Theimplant of claim 12, wherein said implant has a width from one of saidsides to the other of said sides, the height of said implant being lessthan the width of said implant.
 24. A spinal implant comprising: aleading end and a trailing end opposite said leading end, said implanthaving a length from said leading end to said trailing end, saidtrailing end having a perimeter, said trailing end having a holetherein, said trailing end having a slot portion intersecting oneportion of the perimeter of said trailing end, said trailing end havinganother slot portion intersecting another portion of the perimeter ofsaid trailing end opposite said one portion of the perimeter of saidtrailing end, said trailing end being convex; and opposite sides betweensaid leading and trailing ends, said implant having a heightperpendicular to the length of said implant.
 25. The implant of claim24, wherein said slot portion and said another slot portion are oppositeends of a slot having a length and a width transverse to the length ofsaid slot.
 26. The implant of claim 25, wherein said hole has adiameter, the width of said slot being greater than the diameter of saidhole.
 27. The implant of claim 25, wherein said slot of said trailingend is rectangular.
 28. The implant of claim 25, wherein the length ofsaid slot is greater than the width of said slot.
 29. The implant ofclaim 25, wherein said slot has a depth perpendicular to the length andthe width of said slot, the width of said slot being greater than thedepth of said slot.
 30. The implant of claim 24, wherein said hole isthreaded.
 31. The implant of claim 25, wherein said hole has a diameter,the diameter of said hole being less than one half the length of saidslot.
 32. The implant of claim 24, further comprising an opening throughsaid implant and oriented along the height, said opening being betweensaid opposite sides and between said leading and trailing ends.
 33. Theimplant of claim 32, wherein said sides have at least one opening incommunication with said opening oriented along the height of saidimplant.
 34. The implant of claim 32, wherein said implant comprises asecond opening through said implant and oriented along the height, saidsecond opening being between said opposite sides and between saidleading and trailing ends.
 35. The implant of claim 24, wherein saidimplant has a width from one of said sides to the other of said sides,the height of said implant being less than the width of said implant.36. A spinal implant comprising: a leading end and a trailing endopposite said leading end, said implant having a length from saidleading end to said trailing end, said trailing end having a perimeter,said trailing end having a hole therein, said hole having a diameter,said trailing end having a slot portion intersecting one portion of theperimeter of said trailing end, said trailing end having another slotportion intersecting another portion of the perimeter of said trailingend opposite said one portion of the perimeter of said trailing end,said slot portion and said another slot portion being opposite ends of aslot having a length, said slot having a width transverse to the lengthof said slot, the width of said slot being greater than the diameter ofsaid hole; and opposite sides between said leading and trailing ends,said implant having a height perpendicular to the length of saidimplant.
 37. The implant of claim 36, wherein said slot of said trailingend is rectangular.
 38. The implant of claim 36, wherein the length ofsaid slot is greater than the width of said slot.
 39. The implant ofclaim 36, wherein said slot has a depth perpendicular to the length andthe width of said slot, the width of said slot being greater than thedepth of said slot.
 40. The implant of claim 36, wherein said hole isthreaded.
 41. The implant of claim 36, wherein the diameter of said holeis less than one half the length of said slot.
 42. The implant of claim36, further comprising an opening through said implant and orientedalong the height, said opening being between said opposite sides andbetween said leading and trailing ends.
 43. The implant of claim 42,wherein said sides have at least one opening in communication with saidopening oriented along the height of said implant.
 44. The implant ofclaim 42, wherein said implant comprises a second opening through saidimplant and oriented along the height, said second opening being betweensaid opposite sides and between said leading and trailing ends.
 45. Theimplant of claim 36, wherein said implant has a width from one of saidsides to the other of said sides, the height of said implant being lessthan the width of said implant.
 46. The implant of claim 36, whereinsaid implant includes a top and a bottom between said leading andtrailing ends, and between said opposite sides, said top and said bottombeing generally parallel relative to one another.
 47. A spinal implantcomprising: a leading end and a trailing end opposite said leading end,said implant having a length from said leading end to said trailing end,said trailing end having a perimeter, said trailing end having a holetherein, said trailing end having a slot portion intersecting oneportion of the perimeter of said trailing end, said trailing end havinganother slot portion intersecting another portion of the perimeter ofsaid trailing end opposite said one portion of the perimeter of saidtrailing end, said slot portion and said another slot portion beingopposite ends of a slot having a length, said slot having a widthtransverse to the length of said slot, said slot having a depthperpendicular to the length and the width of said slot, the width ofsaid slot being greater than the depth of said slot; and opposite sidesbetween said leading and trailing ends, said implant having a heightperpendicular to the length of said implant.
 48. The implant of claim47, wherein said slot of said trailing end is rectangular.
 49. Theimplant of claim 47, wherein the length of said slot is greater than thewidth of said slot.
 50. The implant of claim 47, wherein said hole isthreaded.
 51. The implant of claim 47, wherein said hole has a diameter,the diameter of said hole being less than one half the length of saidslot.
 52. The implant of claim 47, further comprising an opening throughsaid implant and oriented along the height, said opening being betweensaid opposite sides and between said leading and trailing ends.
 53. Theimplant of claim 52, wherein said sides have at least one opening incommunication with said opening oriented along the height of saidimplant.
 54. The implant of claim 52, wherein said implant comprises asecond opening through said implant and oriented along the height, saidsecond opening being between said opposite sides and between saidleading and trailing ends.
 55. The implant of claim 47, wherein saidimplant has a width from one of said sides to the other of said sides,the height of said implant being less than the width of said implant.56. An artificial spinal fusion implant comprising: a leading end and atrailing end opposite said leading end, said implant having a lengthfrom said leading end to said trailing end, said implant having aheight; opposite sides between said leading and trailing ends, saidimplant having a maximum width from one of said sides to the other ofsaid sides, said implant having a maximum height less than the maximumwidth of said implant; and a plurality of openings through said implantand oriented along the height, said openings being between said oppositesides and between said leading and trailing ends.
 57. The implant ofclaim 56, wherein at least a portion of said leading end is tapered. 58.The implant of claim 56, wherein said leading end is convex.
 59. Theimplant of claim 56, wherein said trailing end is convex.
 60. Theimplant of claim 56, wherein said trailing end includes an opening. 61.The implant of claim 60, wherein said opening of said trailing end isthreaded.
 62. The implant of claim 56, wherein said trailing end has aflat middle portion.
 63. The implant of claim 62, wherein said trailingend includes a rounded portion on both sides of said flat portion. 64.The implant of claim 62, wherein said flat portion includes an opening.65. The implant of claim 64, wherein said opening of said flat portionis threaded.
 66. The implant of claim 56, wherein said trailing endincludes a threaded opening having a central longitudinal axis, saidimplant further including a second threaded opening having a centrallongitudinal axis perpendicular to the central longitudinal axis of saidthreaded opening of said trailing end.
 67. The implant of claim 56,wherein said trailing end includes a trough.
 68. The implant of claim67, wherein said trough is at a middle portion of said trailing end. 69.The implant of claim 67, wherein said trough includes a hole.
 70. Theimplant of claim 56, wherein said sides are generally flat.
 71. Theimplant of claim 56, wherein one of said sides has at least one openingin communication with at least one of said openings oriented along theheight of said implant.
 72. The implant of claim 71, wherein said one ofsaid sides includes a plurality of openings.
 73. The implant of claim56, wherein one of said sides has at least one opening in communicationwith at least one of said openings oriented along the height of saidimplant, said at least one side opening having a central longitudinalaxis and a cross-sectional size transverse to the central longitudinalaxis of said at least one side opening, the transverse cross-sectionalsize of said at least one side opening being different from thetransverse cross-sectional size of at least one of said openingsoriented along the height of said implant.
 74. The implant of claim 56,wherein said implant has a cross section along at least a portion of thelength of said implant that forms a quadrilateral.
 75. The implant ofclaim 56, wherein a portion of said leading end forms an arc of a firstcircle from side to side and a portion said trailing end forms an arc ofa second circle from side to side, the first and second circles eachhaving a radius that is different from one another.
 76. The implant ofclaim 75, wherein the radius of the first circle is less than the radiusof the second circle.
 77. The implant of claim 56, wherein said implantincludes a top and a bottom, each of said top and said bottom having aninterior surface, the interior surfaces of said top and said bottombeing spaced apart from one another to define a hollow interior incommunication with at least one of said openings.
 78. The implant ofclaim 56, further comprising a material adapted to fill at least aportion of at least one of said openings.
 79. The implant of claim 78,wherein said material is adapted to be retained within said at least oneof said openings.
 80. The implant of claim 56, wherein said trailing endhas a middle portion, each of said sides and said middle portion of saidtrailing end having an upper edge, a portion of said upper edges of saidsides and a portion of said upper edge of said middle portion of saidtrailing end lying generally in a plane.
 81. The implant of claim 56,wherein said implant includes a central vertical axis and each of saidsides and said trailing end have an upper portion, said openings havingan upper portion between said upper portions of said opposite sides,said upper portion of at least one of said openings having a minimumdimension transverse to the central vertical axis of said implant thatis greater than the maximum height of said implant.
 82. The implant ofclaim 56, wherein said openings have a central longitudinal axis and aperimeter surrounding the central longitudinal axis, the perimeter of atleast one of said openings being arcuate.
 83. The implant of claim 56,wherein said implant includes a central vertical axis and each of saidsides and said trailing end have an upper portion, said openings havingan upper portion between said upper portions of said opposite sides,said upper portion of at least one of said openings having a minimumdimension transverse to the central vertical axis of said implant thatis greater than a majority of the maximum width of said implant.
 84. Theimplant of claim 56, wherein said implant includes a central verticalaxis and each of said sides and said trailing end have an upper portion,said openings having an upper portion between said upper portions ofsaid opposite sides, said upper portion of at least one of said openingshaving a minimum dimension transverse to the central vertical axis ofsaid implant that is greater than a majority of the length of saidimplant.
 85. The implant of claim 56, wherein at least a portior of atleast one of said openings extends along a vertical line along theentire height of said implant.
 86. An artificial spinal fusion implantcomprising: a leading end and a trailing end opposite said leading end,said implant having a length from said leading end to said trailing end;opposite sides between said leading and trailing ends, each of saidsides and said trailing end having an upper portion, said implant havinga maximum width from one of said sides to the other of said sides, saidimplant having a central vertical axis perpendicular to the length andwidth of said implant, said implant having a height, said implant havinga maximum height less than the maximum width of said implant; and anopening through said implant and oriented along the height, said openingbeing between said opposite sides and between said leading and trailingends, said opening having an upper portion between said upper portionsof said opposite sides, said upper portion of said opening having aminimum dimension transverse to the central vertical axis of saidimplant that is greater than the maximum height of said implant.
 87. Theimplant of claim 86, wherein said opening has a central longitudinalaxis that is generally coaxial with the central vertical axis of saidimplant.
 88. The implant of claim 86, wherein at least a portion of saidleading end is tapered.
 89. The implant of claim 86, wherein saidleading end is convex.
 90. The implant of claim 86, wherein saidtrailing end is convex.
 91. The implant of claim 86, wherein saidtrailing end includes an opening.
 92. The implant of claim 91, whereinsaid opening of said trailing end is threaded.
 93. The implant of claim86, wherein said trailing end includes a middle portion that is flat.94. The implant of claim 93, wherein said trailing end includes arounded portion on both sides of said flat portion.
 95. The implant ofclaim 93, wherein said flat portion includes an opening.
 96. The implantof claim 95, wherein said opening of said flat portion is threaded. 97.The implant of claim 86, wherein said trailing end includes a trough.98. The implant of claim 97, wherein said trough includes a hole. 99.The implant of claim 86, wherein said sides are generally flat.
 100. Theimplant of claim 86, wherein one of said sides has at least one openingin communication with said opening oriented along the height of saidimplant.
 101. The implant of claim 100, wherein said one of said sidesincludes a plurality of openings.
 102. The implant of claim 86, whereinone of said sides has at least one opening in communication with saidopening oriented along the height of said implant, said at least oneside opening having a central longitudinal axis and a cross-sectionalsize transverse to the central longitudinal axis of said at least oneside opening, the transverse cross-sectional size of said at least oneside opening being different from the transverse cross-sectional size ofsaid opening oriented along the height of said implant.
 103. The implantof claim 86, wherein said implant has a cross section along at least aportion of the length of said implant that forms a quadrilateral. 104.The implant of claim 86, wherein a portion of said leading end forms anarc of a first circle from side to side and a portion said trailing endforms an arc of a second circle from side to side, the first and secondcircles each having a radius that is different from one another. 105.The implant of claim 104, wherein the radius of the first circle is lessthan the radius of the second circle.
 106. The implant of claim 86,wherein said implant includes a top and a bottom, each of said top andsaid bottom having an interior surface, the interior surfaces of saidtop and said bottom being spaced apart from one another to define ahollow interior in communication with said opening.
 107. The implant ofclaim 86, further comprising a matorial adapted to fill at least aportion of said opening.
 108. The implant of claim 107, wherein saidmaterial is adapted to be retained within said opening.
 109. The implantof claim 86, further comprising a second opening oriented along theheight of said implant and between said opposite sides and between saidleading and trailing ends.
 110. The implant of claim 86, wherein saidopening has a central longitudinal axis and a perimeter surrounding thecentral longitudinal axis, the perimeter of said opening being arcuate.111. The implant of claim 86, wherein said minimum transverse dimensionof said upper portion of said opening is greater than a majority of themaximum width of said implant.
 112. The implant of claim 86, whereinsaid minimum transverse dimension of said upper portion of said openingis greater than a majority of the length of said implant.
 113. Theimplant of claim 86, wherein said upper portion of said opening has amaximum dimension transverse to the central vertical axis of saidimplant that is less than the maximum width of said implant.
 114. Theimplant of claim 86, wherein at least a portion of said opening extendsalong a vertical line along the entire height of said implant.
 115. Anartificial spinal fusion implant comprising: a leading end and atrailing end opposite said leading end, said implant having a lengthfrom said leading end to said trailing end and a maximum widthperpendicular to the length; a top and a bottom between said leading andtrailing ends, said implant having a maximum height from said top tosaid bottom, said implant having a central vertical axis through saidtop and said bottom; a plurality of openings in each of said top andsaid bottom; said top and said bottom being spaced apart from oneanother to form an open area therebetween, said openings in said top andbottom being in communication with said open area; the maximum width ofsaid implant being greater than the maximum height of said implant. 116.The implant of claim 115, wherein at least a portion of said leading endis tapered.
 117. The implant of claim 115, wherein said trailing end isconvex.
 118. The implant of claim 115, wherein said implant has a crosssection along at least a portion of the length of said implant thatforms a quadrilateral.
 119. The implant of claim 115, wherein a portionof said leading end forms an arc of a first circle from side to side anda portion said trailing end forms an arc of a second circle from side toside, the first and second circles each having a radius that isdifferent from one another.
 120. The implant of claim 119, wherein theradius of the first circle is less than the radius of the second circle.121. The implant of claim 115, further comprising a material adapted tofill at least a portion of one of said openings in said top.
 122. Theimplant of claim 121, wherein said material is adapted to be retainedwithin said one of said openings in said top.
 123. The implant of claim115, wherein one of said openings in said top has a minimum dimensiontransverse to the central vertical axis of said implant that is greaterthan the maximum height of said implant.
 124. The implant of claim 115,wherein at least one of said openings has a central longitudinal axisand a perimeter surrounding the central longitudinal axis, the perimeterof said opening being arcuate.
 125. The implant of claim 115, whereinone of said openings in said top has a minimum dimension transverse tothe central vertical axis of said implant that is greater than amajority of the length of said implant.
 126. The implant of claim 115,wherein at least one of said openings in said top and at least one ofsaid openings in said bottom overlap each other along a vertical line.127. The implant of claim 115, wherein said trailing end has a middleportion, said top having an outer perimeter at said middle portion ofsaid trailing end and at opposed side portions, the outer perimeter ofsaid top at said opposed side portions and at said middle portion ofsaid trailing end lying generally in a plane.
 128. The implant of claim115, wherein said top and said bottom are generally parallel to oneanother.
 129. The implant of claim 115, wherein at least one of said topand said bottom is generally planar.
 130. The implant of claim 115,wherein at least one of said top and said bottom is non-arcuate fromside to side.
 131. The implant of claim 115, wherein at least one ofsaid top and said bottom includes a portion extending across the entirelength of said implant generally halfway along the maximum width of saidimplant.
 132. The implant of claim 115, wherein said open area has amaximum width transverse to the length of said implant the maximum widthof said open area being greater than the maximum height of said implant.133. The implant of claim 115, wherein each of said openings in said topand said bottom has a central longitudinal axis and a maximum dimensiontransverse to the central longitudinal axis of said opening, said openarea having a maximum width transverse to the length of said implant,the maximum width of said open area being greater than the maximumtransverse dimension of one of said plurality of openings in one of saidtop and bottom.